Thanks Simon. I figured that even though this diverts me from other 'in progress' stuff, so what?
I like having a choice of things to work on.
I built the turntable today. I decided to use one of the older, thicker style CD cases because it has a stronger center section and holds the CD more firmly. I removed the liner from the case and trimmed and sanded it smooth on top. A CD case holds the CD up off the bottom to protect the surface of the CD. This allows a lot of wobble, so I fixed that. I took another CD (just the right thickness and CHEAP) and cut the center of it out to fit over the raised center section of the case. This allows the cut CD to fit firmly on the bottom of the case and provide a good, flat support for the turntable CD. Note that the bottom of a CD has a tiny raised ridge around that cutout area. I sanded this flat on BOTH the base CD and the TT CD (TurnTable CD) so they would sit perfectly flat on each other.
After trimming the base CD, I used CA to glue it firmly into the case. Then I took an old Tyco road crossing track and cut it to fit the TT CD.
The MOST WONDERFUL
Dental tool was used to carve out clearance on the bottom of the track for the center of the CD case, so the track would fit flat onto the TT CD.
Then the track was glued in place with more CA.
After the glue set, I snapped the TT onto the base and it is PERFECT! No wobble, holds nice and tight. Now to sink it into the foamcore top. Time for commitment to the plan.
The base foam is laminated, 2" thick. The foamcore top is 3/16". That means I'll have to laminate a thin foam section under the top so the TT can be set deep enough without digging into the 2" layer. That puts the surface about 2-9/16" above MBT. (Mean Board Top)